1. Field of the Invention
The invention relates to a lighting device to be used for a liquid crystal display device and including an electroluminescence device a liquid crystal device including the lighting device, and a method of fabricating the lighting device.
2. Description of the Related Art
A conventional lighting device used in a liquid crystal display device was generally designed to include a transparent optical inductor such as an acrylic plate, and a fluorescent tube or a light emitting diode arranged on an end surface of the optical inductor. Such a lighting device can be grouped into a front-light type lighting device used for a reflection type liquid crystal display device, and a back-light type lighting device used for a transmission type or a combination type liquid crystal display device. The front-light type lighting device is positioned in front of the reflection type liquid crystal display device, and emits a light to the liquid crystal display device, whereas the back-light type lighting device is positioned at the rear of the transmission or combination type liquid crystal display device, and emits a light through a back of the liquid crystal display device.
The reflection type liquid crystal display device including the front-light type lighting device is disclosed, for instance, in Japanese Unexamined Patent Publications Nos. 2000-29008, 2000-19330 and 11-326903.
Hereinbelow is explained a structure of the reflection type liquid crystal display device including the front-light type lighting device, disclosed in Japanese Unexamined Patent Publication No. 2000-29008, as a typical one.
FIG. 1 illustrates a conventional front-light type lighting device used for a reflection type liquid crystal display device.
The front-light type lighting device 110 is comprised of a linear light source 111, a reflector 109 in which the linear light source 111 is located, an optical conductor 112 through which a light emitted from the light source 111 is introduced into a liquid crystal display device (not illustrated), and a protector 113 located above an upper surface of the optical conductor 112.
The linear light source 111 is comprised of a plurality of cold cathode ray tubes or light-emitting diodes arranged in a line, and is spaced away from an end surface 112a of the optical conductor 112. The optical conductor 112 is formed at an upper surface or a reflection surface 112b at which a light emitted from the light source 111 is reflected, with a sawtooth.
In operation, a light emitted from the light source 111 enters the optical conductor 112 through the end surface 112a, is reflected at the reflection surface 112b, and leaves the optical conductor 112 through a lower surface 112c. 
An example of a reflection type liquid crystal display device including a back-light type lighting device is disclosed, for instance, in “Monthly Display”, May 1996, pp. 35. FIG. 2 illustrates an example of a reflection type liquid crystal display device including a back-light type lighting device.
A back-light type lighting device 130 is comprised of a light source 111, a reflector 109 in which the linear light source 111 is located, an optical conductor 112 through which a light emitted from the light source 111 is introduced into a liquid crystal display device (not illustrated), a reflector 131 making close contact with a lower surface 112b of the optical conductor 112 for reflecting a light emitted from the light source 111, a diffusion plate 134 facing an upper surface 112c of the optical conductor 112, a first lenticular lens 132 located in parallel with the diffusion plate 134, and a second lenticular lens 133 located between the diffusion plate 134 and the first lenticular lens 132.
The diffusion plate 134 and the first and second lenticular lens 132 and 133 ensure that a light having been introduced in the optical conductor 112 effectively leaves the optical conductor 112 through the upper surface 112c, and further widen a viewing angle.
In operation, a light emitted from the light source 111 enters the optical conductor 112 through an end surface 112a, is reflected at the lower surface 112b of the optical conductor 112, and leaves the optical conductor 112 through the upper surface 112c into a liquid crystal display device (not illustrated) through the first and second lenticular lens 132 and 133.
For instance, Japanese Unexamined Patent Publication No. 10-50124 has suggested a lighting device including an organic electroluminescence device as a light source, and an optical conductor through which a light emitted from the electroluminescence device is introduced into a liquid crystal display device. The electroluminescence device is spaced away from an end surface of the optical conductor.
In all of the above-mentioned conventional lighting devices, a light source and an optical conductor are fabricated separately from each other, and then, they are adhered to each other. In such a structure, it would be unavoidable that some spacing is generated between the light source 111 the end surface 112a of the optical conductor 112.
As illustrated in FIG. 1, lights emitted from the light source 111 are not always introduced into the optical conductor 112. Though about 30% of the lights are surely introduced into the optical conductor 112 as indicated with an arrow 107, about 70% of the lights are not introduced into the optical conductor 112 as indicated with arrows 108.
A light required for illuminating a liquid crystal display device is fixed in an amount. The lost lights indicated with arrows 108 cause an increase in power consumption. Since almost all power consumption is made by the lighting device in a liquid crystal display device, power loss caused by the lost lights would pose a problem that a lifetime of a battery is much shortened in a case where a liquid crystal display device is used in a handy communication device such as a cellular phone.
Japanese Unexamined Patent Publication No. 10-268308 has suggested a lighting device including a light source, and an optical conductor through which a light emitted from the light source is introduced to a target. The lighting device is arranged in front of the target. The optical conductor includes a first optical sub-conductor having a first surface through which a light emitted from the light source enters the optical conductor, and a second optical sub-conductor having a second surface through which the light leaves the optical conductor to the target. The first optical sub-conductor introduces the light to the second optical sub-conductor, which allows the light to pass therethrough in a direction normal to the second surface.
Japanese Unexamined Patent Publication No. 11-202799 has suggested a reflection type liquid crystal display device including a reflection type liquid crystal panel, an optical conductor which reflects a light emitted from a light source, in a thickness-wise direction thereof for illuminating the liquid crystal display panel, and a linear organic electroluminescence device. The organic electroluminescence device is comprised of a linear transparent electrode facing an end surface of the optical conductor, and patterned in a width smaller than a thickness of the optical conductor, a metal electrode which mirror-reflects a light and has a width greater than a width of the linear transparent electrode, an organic electroluminescence material located between the transparent electrode and the metal electrode.
Japanese Unexamined Patent Publication No. 11-326898 has suggested a reflection type liquid crystal display device including a liquid crystal layer sandwiched between a pair of substrates facing each other, a liquid crystal display element having a reflector on one of the substrates, a plate-shaped optical conductor arranged on the other of the substrates, a light source positioned adjacent to an end surface of the optical conductor, and a plurality of transmission dots three-dimensionally formed on a principal surface of the optical conductor adjacent to the liquid crystal display element, and having a mirror surface as a top surface in parallel with the principal surface.
Japanese Unexamined Patent Publication No. 2000-155315 has suggested a front-light type lighting device including a light source, and an optical conductor having an end surface through which a light emitted from the light source enters the optical conductor, and a first surface perpendicular to the end surface, through which the light leaves the optical conductor. A device for allowing a particular polarized light to pass the optical conductor is adhered to the first surface of the optical conductor such that a light is not reflected at an interface between the device and the optical conductor.
However, the above-mentioned problem remains unsolved even in the above-mentioned Publications.